Cause He'll Fit
by Mezclau
Summary: He had to stop thinking like that. She had to stop thinking like that. They were just partners. Right?


**Hi! This is my first-ever fanfiction, so I apologize in advance. however, any reviews would be very helpful and much appreciated! It's a little long, but hopefully you'll enjoy it...**

DISCLAIMER: definitely don't own them.

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><p>Beckett knew she shouldn't have opened the door. Not after a case like that. But if Kate Beckett knew anything, she knew that with Richard Castle standing outside her door, the alternative was monumentally worse.<p>

So she opened it, laundry basket in hand—she had been cleaning up from the week.

As soon as she did, of course, she was greeted by Castle's mock-dumbfounded expression and the quickening of her own heartbeat.

"Why Detective, I wouldn't have expected you to be up so late. I would've thought the fine Detective Beckett got the full eight hours after such a serious case."

"Well Castle, looks like you don't know me so well after all. And if you didn't expect me to be awake, why were you pounding on my door?"

"To wake you up, of course. Everyone knows you can't knock quietly if you want to wake someone up."

"And you couldn't have thought of another way to wake me up? Guess you're not good as I would've thought…."

Kate knew she had gone too far the second the words left her tongue. Damn. Castle would never let this one go.

"In fact, my dear detective, I can think of plenty of ways to wake you up, should I ever be in that position. Though tonight you seem to be having trouble sleeping…You know, I can also think of plenty of things to tire you out—"

The words died on Castle's tongue as he caught sight of Kate's expression.  
>"Castle," she reprimanded, a warning tone to her voice. "You still haven't explained why you're here."<p>

"Whatever do you mean?"

"I mean, Castle,"—ouch, that warning tone was back, and it sounded more like scolding this time.

"Why have you chosen to appear in my doorway at,"—she checked her father's watch—"twelve-oh-three at night after spending the majority of the last thirty-six hours with us, all of which ended just,"—she did some mental math—forty-three minutes ago? Some people do a thing called sleep, you know."

"Correction, Detective. It's 12:03 in the morning."

Kate rolled her eyes, but Rick continued.

"And as a matter of fact I'm quite familiar with sleep. However, I'm also quite familiar with the sleep patterns of a certain detective. More specifically, the lack of sleep patterns. Or sleep at all for that matter."

Beckett rolled her eyes again.

"So I came over here to ensure that you were taking care of—things."

He drifted off as he caught sight of the laundry basket in her hands. More specifically, of the contents of the laundry basket. Particularly, of the lacy black peeking out around the corner of one of Kate's NYPD t-shirts.

Right, Rick. NYPD. The precinct. The case they had only solved after Ryan quadruple checking the lawyer's financial records, and even then only on Beckett's interrogation skills.

Right. Beckett. Not Kate. Work. Why was he here anyway? It wasn't like she would ever—"Uh, is this 407?"

Castle was drawn out of his reverie by the pizza guy's voice and turned to meet him, catching Kate's expression as he did. Right, he forgot about that part. Should probably have gotten to that part of the conversation earlier. But he could deal with that later. Right now, the aroma of melted cheese on bread was too captivating.

"Ah—Right. There you are," Castle stammered eloquently as the box and the money shifted hands. The delivery boy returned his change, wishing the couple—no, not a couple. Wishing the _two_ a nice night—as he turned down the stairwell.

"You ordered a pizza. To my house. At midnight."

"Well, I was simply ravenous on the way home, and the half of my mother's leftover chicken breast I grabbed on the way to get cleaned up did absolutely nothing. So while I was in the shower I was thinking about you—"

Woah. Not there Castle, not yet. Possibly never, if he kept up like this.

Kate could tell Castle was already reprimanding himself, but continued with her disapproving look.

"Why Kate Beckett, I never. I assure you, my thoughts tonight were of an entirely innocent nature. Thought I can't say the same about a few other nights…" Castle's eyes drifted upward, seemingly lost in thought.

"You know what, fine Castle. Whatever. Come in."

Kate stepped backward as to allow Rick and his pizza box in. His pizza box—containing what smelled like a wonderful, wonderful pizza to a woman who had only eaten a granola bar or two and half a bagel grabbed at the precinct that day. That wonderful, wonderful pizza, from that wonderful, wonderful man…Her eyes drifted toward Castle's, green catching blue as they drew closer.  
>Kate's breath quickened. But she had nothing if not self control, so she shook herself out of it and moved away from the doorway. What was she thinking? She sounded like a teenager. Felt like one too, on occasion. But not tonight. Just pizza tonight.<p>

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><p>Forty-five minutes later Kate Beckett was staring at Richard Castle loading her dishwasher as she sat on the couch, thinking how natural he looked, how the countertops came to just the right height for his elbows to rest, how—well, how well he just <em>fit<em> into her kitchen.

Her whole apartment, as a matter of fact. Perhaps it was a side affect of studying her for the past four years, but earlier he had gone to connect his iPhone to her speakers—poking through her music collection as he did—and just seemed to know where to find it, along with the exact steps of the path Kate herself usually took to get there.

That was another thing—looking through her music, traipsing around her house, loading her dishwasher? All things the Kate she knew would have absolutely detested, things she would have never allowed. Then again, the Kate she knew would have never even let him into her apartment. Much less into her life. But Rick just—just fit there, and now she couldn't imagine her days without him.

Suddenly, a memory was triggered from deep within—Kate had walls to keep these things in, locks to keep them from never escaping during the wrong moment, but evidently, they were malfunctioning tonight.

_A young Kate Beckett looked up at her mom as she got ready for dinner with her father. Johanna Beckett was gorgeous, that much Kate had known since before she could remember.  
>"Mommy, how come you and Daddy are having dinner at home, but I'm not allowed to be here?"<em>

_Johanna smiled, amused by the innocence of her daughter's question. _

"_Because we love each other sweetie, and sometimes grown-ups want some privacy."_

"_But how come you're not going out to a rest-raunt?" _

"_Well, honey, that's the privacy part. All I really need is your daddy to have a good night, not fancy food or waiters and menus."_

"_Because you love him special?"_

"_Yes Katie, because I love him special. You'll understand one day, when you meet someone you love special too."_

"_Mommy? How am I s'possed to know if I love someone _special_, or just regular?"_

"_Well honey, it's different for everyone. But I knew with your dad, he just seemed to fit into my life. One day I just realized that it clicked with him. I loved him special."_

_Kate contemplated this for a moment—it was pretty heavy stuff for a six-year-old. _

"_But what if I don't know? You always know what I'm feeling Mommy. Will you tell me?"_

_Johanna laughed quietly. "Of course sweetie. But I'm pretty sure you'll know on your own, too."_

"'_Cause he'll fit?"  
>"'Cause he'll fit."<em>

* * *

><p>"So which one?"<p>

Kate started as Rick's words pulled her out of the memory. She looked up at him, still lost in the last edges of the scene and her mother's words.

"Uh. Sorry?"

"Which movie?"

Kate hadn't planned on the dinner being extended into a move night, but somehow couldn't bring herself to deny the blue eyes shining excitedly into hers.

There might've been other things preventing her from rejecting him as well, but she wasn't sure if she was ready to fully delve into _those_ thoughts just yet. Especially not like this. Especially not—not when he looked like that.

"Fine, I'll pick if you won't. 'Superman IV: The Quest for Peace' sounds good…"

"What…Castle!"

"I kid, I kid. 'Forbidden Planet: Director's Cut' good?"

She smiled; still wading out of the sea of emotion the memory of her mother's words had drawn. It _was_ their movie after all. The first they had ever seen together, the only one they could _really _quote back and forth endlessly, the one she would always associate with their—partnership. Not their relationship. They were partners. Nothing more. Of course.

After hooking the movie up Castle turned toward the couch again, noting the look on Kate's face.  
>"Hey…Hey. Kate. You okay?" He paused.<p>

"If…if you don't want me to be here, or…to stay, I—I can leave, or—."

For someone famous for his words, Rick was almost to overcome with fear to force them out. But he had to—for her sake. It was all for her sake.

A few moments passed, Rick still half-perched on the edge of the couch as he watched Kate stare down at her left thumbnail, biting her lip as she did.

God she looked so cute when she did that.

Rick knew he had just offered to leave for the night, but didn't know how that would be possible, as he was all but physically restraining himself from holding her now. Something was wrong with Kate, with _his_ Kate. And he wanted more than anything in the world to fix it, to fix everything for her; he would hold the entire world up by himself if it would take even one quarter of the weight off of her shoulders.

Kate blinked twice, glancing up at Rick as she did. She was startled by the look on his face —but not frightened, why wasn't she frightened?

It was an expression she had only seen on very specific people's faces in very specific situations before—her father, when he first saw a photo of himself and her mother they discovered last month; Ryan, when he saw Jenny at the end of the aisle a few weeks ago, and the writer from that superhero case when he saw Officer Hastings.

It was an expression of pure love, that's the only way she could describe it. And that startled her. He couldn't look like that. Not Castle. Not now.

Kate realized he was still waiting on her answer.

"No! Don't leave—stay. We—we can start the movie."

Castle relaxed, feeling the apprehension rolling off of him in waves.

"Of course."

Rick reached for the remote control on the coffee table, pressing play as he slid in—too close, way too close for either of them—next to her.

Kate could feel the heat radiating off of him, and noted how she immediately began to warm up as he settled in. Like he balanced her. 'Of course,' said a voice in the back of her head. 'He does.'

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><p>Feeling brave an hour or so later, Rick slid his arm underneath the detective's back, allowing her to lean into him. Kate knew she should stop the whole thing, knew she should have stopped it all a long time ago.<p>

But it was late, and their case was hard, and she was tired. The combination of good pizza, good wine, and good company combined to overwhelm her senses and she leaned toward Rick of her own accord.

He had opened the door—but she walked through herself.

Soon after, Rick felt his detective's sleeping head fall down onto his shoulder, thinking as he realized what had happened that this was it—what everyone talked about all these years.

Rick had never felt that true 'connection' with Meredith or Gina.

Sure, he loved them; while they were together, he even liked them most of the time. But he wasn't _in_ love with them, and until a few years ago he figured that the whole soulmate thing was all a myth, a widespread conspiracy to distract people from the rigors of everyday life.

And then, he met Kate.

Rick Castle knew his reputation. He even perpetuated it. But the reality was that he didn't have nearly as many conquests as the press would like to believe, and none in the last four years—since Kate.

With her it was different—she captivated him night and day, she matched his intellect and understood his wit. She knew him better than he knew himself some days, and he hoped that he was even half the—the partner to her as she was to him.

Rick had always shied away from thoughts of 'forever and always' before, never feeling the need for weddings and families and phone calls every few hours just to update the other on the day's events.

But Kate Beckett changed his definition of always. He wanted to know everything she did all day, wanted to share the minute details of the most boring parts of his life with her. He couldn't imagine ever being attracted to anyone else, couldn't imagine ever having even a _similar_ relationship with anyone else.

But Kate wasn't ready yet. So he would wait until she was—however long that took. For tonight, this was good enough.

In a move he perfected from years of movie watching with a sleepy Alexis, he reached around Kate with his other hand and moved the pillows away, then leaned over to swing her legs up to the couch and her head down to his lap without waking her. And he succeeded—Kate barely stirred.

So Richard Castle leaned back, covering her hand with one of his as he lowered the volume. He would watch the last forty minutes of the movie alone, because he would do anything to maintain the look of peace on Kate's face.

She really was beautiful, he realized yet again as he stared down at her. Rick imagined he would spend the majority of those forty minutes—and beyond—watching her instead of the movie.

But that was okay. Because Katherine Beckett's head was in his lap in the middle of her apartment. Because they had eaten dinner together, and talked over the case. Because she had let him reassure her about her perceived failings over the last few days, and hopefully let some of it sink in. Because they watched their movie together, and she had fallen asleep on his shoulder.

Rick didn't know what would happen after the movie ended, or if she woke up before it did. He didn't know what would happen the next day, or the next year, or in ten years, or twenty.  
>But he knew he had Kate for now. And he knew that if he could only hang on to her, the rest would all fall into place. After all, she fit perfectly—in his lap, and in his life.<p>

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><p><strong>Thoughts? Sorry if it tended toward too much 'friendship' in this chapter, later ones will head back toward 'romance' and 'hurtcomfort', I promise!  
>R&amp;Rs would be fantastic :)<strong>

Also, I want to write more for Castle, but have trouble coming up with ideas. If anyone has any they'd like to see as a fic, PM me or leave a review and let me know!


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